30 August 2007

Coax Change on the Beam

Last weekend I continued the antenna work theme by doing some maintenance on my own setup. I have a 3-element 4-band beam on a 30-foot tower that has been giving some poor SWR readings lately. I decided to start with the coax since the line that was up there was 12-year old Radio Shack RG8, and the Tucson sun and monsoon rains can really wreak havoc on just about anything.I had a couple of lines of Times Microwave LMR400 laying up on the roof, attached to a VHF beam that is currently out of service, so I decided the easiest approach would be to just swap the lines. I climbed the tower and it took me about an hour to make the changeout. While I was up there I noticed that the fiberglass insulators used on the Cushcraft antennas (I also have a small VHF/UHF vertical) were really trashed.Anyway the change in transmission line seems to have helped quite a bit but I still have an unacceptably high SWR on 10 and 15 meters. 20 and 40 are just fine. I'm guessing there is a problem with the traps but it's going to be a big job to repair or replace the antenna.It's a bummer that while the antenna is arguably the most important part of any ham radio installation, it's also the most difficult to maintain.

About KR7RK

I'm an Amateur Extra class operator. I serve as Treasurer of 10-10 International Net, and enjoy working many different bands and modes. I operate from my home as well as mobile. You can read more about me on my website at http://www.kr7rk.com